Conversion of hydrocarbons



March 19, 1940. H. v, ATwELL cNvERsIoN 0F HYDRocARBoNs Filed Dec. 17, i956 fr o `Patented 19.107940 y CoNvEnsIoN oF HYDROCARBONS* Harold v. Arwen, White Pleinen. Y., assignor to I Process Management Company, Inc., New York,

N'. Y., a corporation of Delaware Application December 17, 193s, serialv No. liesse i 'z claims. .(c'l. 19t-9)` i This invention yrelates to the production of normally liquid hydrocarbons from normally gaseous hydrocarbons and more particularly to a process of treating normally gaseous hydrocarbons to 'producetherefrom gasoline of high antiknock value. g l c The vinvention vcontemplates the thermal conversion or polymerizationof a' stream of normally gaseous hydrocarbons which may include both v olenic and parainic constituents and may be fderived from any,suitable"source,such as natural gas or'the products of oil or gas cracking. The

"conversion reaction products lare treated to separate therefronia fraction consisting of substantial proportions of the relatively vlight norinally liquid hydrocarbons and :normally gaseous hydrocarbons, leaving. a second fraction consist-- ing yof normallyliquid hydrocarbonsin the gasoline boiling rangebut decientin the light ends which ordinarily constitute aporticn of gasoline. Therst-rnentioned' fraction is subjected to conditions favoring selective polymerization, which polymerization andsi'milar; reactions a portion of thefbranch-chain compounds'` contained therein to products of higher molecular Weight in the gasoline boiling range. rIlhe selective conversion reaction products v,and theheavy fraction of the thermal conversion reaction products are treated to producethere'fom a gasolineblehd containing ythe gasoline constituents in both fractions and having the desired proportion of light ends and an increased proportion of heavier. polymers in,- cluding branclnchain polymers. This may be suitably accomplished by blending the said heavy fraction and the preferential conversion reaction products and fractionating theblend'to produce the desired ygasoline fraction therefrom. Any normally gaseous hydrocarbons' having two or 'more carbon atoms per molecule and undersired for the selective conversion Areaction may be separately recovered and returned to the system by adding them to the fresh feed to the thermal conversion step. Gas oil produced in the system may be separately recovered and used as a quench for the thermal polymerization reaction products. If desired, branch-chain oleiinic polymers produced'by the selective conversion reaction may be suitably hydrogenated. y The accompanying drawing isa diagrammatic plan of apparatus suitable for use in carrying out the present invention. y

The invention will be specifically-described with 'reference to the drawing but it is understood that the. ,invention vis not limited Aby 1 the physical maybe catalytic,z to 'preferentially convert by l vlimitations of theapparatus illustrated andis capable of other modifications than v`the onev chosen for purposes of illustration.

In the drawing'. fresh feed, which kconsists of normally gaseous hydrocarbons and may include both olenic and paraiinic constituents, isins troduced to the system through line l, preheated in a heat exchanger 2', land introduced into a polymerization heater 3 wherein it is' subjected to conditions of temperature and pressure to convert a substantial proportion `thereof to normally liquid hydrocarbons.v v For example, the gases may be held under a pressure of 1000 to 2000 pounds and heated to a temperature of 1000" to ll00 F. in the polymerization heater. From the heater 3 the reaction products are Withdrawn through line il, cooled rby the vadrnixture therewith of cooling `fluid through line 50,'. and further cooled by heat exchange with the fresh feed in heat exchanger 2 after having the pressure thereon released through valve 6. Throughnline 4 the reaction products are conducted'to a fractionator 1 after being cooled further, if desired, by a cooler 8. 4

, In the fractionator'l conditions of tempera-ture rand pressure are maintained 'whereby a yliquid vfraction deficient in lighty endsordinarily present in gasoline isv condensed `from the gases and collects in the bottom of the frvactionator '1. The overhead from the fractionator Tis' withdrawn through line 9 and cooler I0 and consists of normally gaseous hydrocarbons and a substantial proportion of the lighter normally liquidhydrocarbons. For example,l the reaction products may be fractionated lvvhereby substantially all the Chydrocarbons are passed overhead through line 9. The overhead gases are further cooled in the cooler luto condense aportion thereof including any undesirably heavy hydrocarbons, which portion is separated in the separator li and returned to the fractionator 'lI as' reflux through line i2 by means of pump I3. The uncondensed gases from the separator il, which include a substantial proportion of `the lighter normally liquid hydrocarbons, such as the C5 hydrocarbons, are conducted through line lli to a second fractionator l5 after further cooling in cooler i6. In the fractionator liii conditions of temperature and pressure are maintained Where- 'by substantially all thev normally yliquid hydrothe C3 and C2 hydrocarbons, or the latter may be excluded from the condensate. 'The condensate from the bottom of the fractionator I5 which consists, for example, of C4 and C5 hydrocarbons, which include both straightand branch-chain constituents, and any desired proportion of the Cs and C2 hydrocarbons is withdrawn through line Il by a pump I8, preheated in a heat exchanger I 9, and passed to a heater 20 which heats the gases to the temperature appropriate for the succeeding conversion step. From the heater 20 the gases are withdrawn through line 2l and passed to a catalytic reaction chamber 22 wherein at least a portion of the branch-chain hydrocarbons contained therein are preferentially converted to hydrocarbons oi higher molecular weight by polymerization and possibly by means of other similar reactions with minimum conversion of the straight-chain hydrocarbons contained therein. In the catalytic reaction chamber 22 conditions of temperature and pressure are maintained and a suitable `catalyst is provided whereby the desired preferential conversion of branch-chain hydrocarbons is accomplished, for example, by means of the preferential polymerization of iso-olens. For example, with a catalyst such as aluminum oxide supported on diatomaceous earth, or aluminum chloride supported on pumice, the temperature may be from 50 to 150 C. at atmospheric pressure with a time of Contact of 3 to 50 seconds depending upon the degree of polymerization desired. With the higher temperatures mentioned moderate pressures of 50 to 100 pounds per square inch are desirable.

The reaction products of the selective conversion reaction pass from the chamber 22 through line 23 in heat exchange with the incoming feed in a heat exchanger I9 and are introduced to a third `fractionator 24 after having been further cooled, if desired, by means of a cooler 25.

The normally liquid fraction separated in the first-mentioned fractionator I is withdrawn through line 26 and adm ixed with the products of selective conversion passing through line 23 from the catalytic reaction chamber 22, and the combined Streams are passed to the fractionator 24 through line 23. In the fractionator 24 conditions of temperature and pressure are maintained whereby a fraction including the gasoline constituents and lighter gases passes overhead through line 2l' and whereby a heavier oil or tar is collected in the bottom of the fractionator 24 and withdrawn as desired through line 28. A side stream consisting substantially of clean gas oil is withdrawn from a trap-out tray in fractionator 24 through line 5, and passed by means of pump 3U for admixture with the hot products of thermal polymerization emerging from polymerization heater 3 inline 4 to quench the reaction products at least partially for preventing further polymerization or other conversion reaction. Gas oil not required for such use may be withdrawn from the trap-out tray and the system through line 3l The overhead from the fractionator 24, withdrawn through line 21, is cooled by means of cooler 32 to condense a portion thereof including undesirably heavy constituents and introduced into a separator 53 wherein the resulting condensate is collected. The condensate in the separator 53 is returned to the fractionator 24 as reflux through line 35 by means of pump 36. Uncondensed gases pass overhead from the separator 53 through line 54 and a cooler 55 and are introduced to a fourth fractionator 33 wherein the gasoline fraction is condensed and stabilized and the undesired light gases are passed overhead. For example, the overhead gases may consist of C3 and lighter hydrocarbons and hydrogen but may also include, if desired, all or a part of the C4 hydrocarbons of the stream. The gasoline fraction is withdrawn from fractionator 33 and from the system through line 34.

The overhead gases from the fractionator 33 are withdrawn through line 31, passed through a cooler 56 to condense a portion thereof including undesirably heavy constituents and introduced to separator 5`I wherein the resulting condensate is collected. This condensate may be returned to the fractionator 33 as reflux through line 5I by means of pump 48. Uncondensed gases pass overhead from the separator 51 through line 3S to a fractionator 40 after being further cooled by means of a cooler 4 I.

The overhead gases from the fractionator I5 are withdrawn through line 38, passed through a cooler 59 to condense a portion thereof including desired heavy constituents and introduced to a separator 6D wherein the resulting condensate is collected. This condensate may be returned tc the iractionator I5 as reux throughline 50 by means of pump 49. Uncondensed gases 'pass overhead from the separator GI) through line 6| and are combined with the gases passing to the fractionator 40 through line 39. If the gases from the separator 6U contain few constituents desired for recycling to the polymerization heater they may be withdrawn from the system through line 62 In the fractionator 40 conditions of temperature and pressure are `maintained whereby hydrogen and methane and any undesired C2 hydrocarbons are separated from the heavier hydrocarbons. The overhead gases consisting principally of hydrogen and methane and undesired C2 hydrocarbons are withdrawn through line 42 and are further cooled by means of refrigeration means 43 to condense a portion thereof including any desired constituents which are separated in separator 44 and returned as reflux to fractionator 40 through line 45 by means of pump 46. The C2 and heavier hydrocarbons desired for the system collect in the bottom of fractionator 40 and are withdrawn through line 4l and combined with the fresh feed passing through line I.

Heating means, such as heating coils 52, may be provided in the bottoms of the fractionators "I, 24, 33, I5 and 40 to maintain the proper temperature of the condensate to prevent the inclusion therein of undesired light components.

The various fractionators are provided with suitable trays or other fractionating equipment whereby the various operations incidental to frac` tionation such as evaporation, absorption. condensation, stripping, etc. occur. Suitable cooling means other than the reiiux means shown may be provided in the tops of the various fractionators as desired to effect any further cooling necessary.

It is apparent that while separate fractionators 24 and 33 have been provided for the separation of gasoline and gas oil and heavier oils from the system this separation may be suitably accomplished in one fractionator of suitable dimensions and provided with an intermediate trapout tray and means for withdrawing liquid collected therein from the fractionator located at a point suitable to effect collection and withdrawal ol' gasoline. This general observation holds true for the other fractionating operations of the system,

a plurality of fractionators having been shown in order to simplify presentation oi the subject matter of the invention. For example, fractionators 'l and l5 could be combined in a single structure With an intermediate trapout tray arranged to effect collection and withdrawal of a liquid consisting of light normally liquid hydrocarbons and normally gaseous hydrocarbons for passage to heater Zil, as described.

Although the specic embodiment oi the invention described above includes the `combination of the Whole liquid fraction from fractionator 1 With the entire product of selective conversion, it is obvious that the gasoline fraction from each maybe separately recovered, after which the recovered fractions are blended in the desired proportions. Furthermore, Where the products are jointly fractionated, as described above, a portion of the reaction products of selective conversion and/or a portion ofthe liquid fraction from fractionator 'i may be separately Withdrawn and separately treated in order to preserve the desired blend in the gasoline produced in fractionator 33.

The4 gasoline produced according to this invention is of superior value in that it does not have an excess of light ends since a portion of these have been selectively converted to liquids of higher boiling point with the result that the gasoline produced in the system has a better balance of high and low boiling point constituents.

Furthermore, the selective conversion of branch- Chain hydrocarbons, such as iso-olens, produces branch-chain higher boiling polymers in the gasoline which improve its anti-knock value.

. The above description relates to a specific embodiment 'of the invention, but it is to be understood that the invention is capable of other modifications and embodiments wherein the light ends of polymerized gasoline together with heavier gases are subjected to polymerizing conditions to preferentially convert branch-chain hydrocarbons such as iso-olefins to products of higher molecular Weight to produce a better balance of low and high boiling constituents in the gasoline and increase the anti-knock value of the gasoline by the inclusion therein of high boiling branch-chain polymers.

I claim: f

l, In the process of converting normally gaseous hydrocarbons to gasoline motor. fuel by heating normally gaseous hydrocarbons under high pressure to eiect substantial conversion thereof to liquid hydrocarbons including a gasoline fraction having a proportion of relatively light lowboiling normally liquid hydrocarbons including olefinic constituents Which ordinarily constitute the light ends of gasoline which is in excess of the proportion of such low-boiling constituents desired in a gasoline of satisfactory boiling'characteristics, the steps of separating from the products of said conversion operation normally liquid hydrocarbons substantially deficient in said light low-boiling normally liquid hydrocarbons and a fraction consisting of substantial yproportions of said light low-boiling normally liquid hydrocarbons and normally gaseous hydrocarbons having four carbon atoms per molecule and substantially free of hydrocarbons having less than four carbon atoms per molecule, subjecting said lastmentioned fraction to polymerizing conditions in the presence oi a polymerizing catalyst to convert olenic constituents thereof to higher boiling hydrocarbons, and blending gasoline constituents of the reaction products of said catalytic polymerization treatment with said normally liquid hydrocarbons deicient in said light lowboiling normally liquid hydrocarbons to produce a gasoline motor fuel o desired boiling characteristics. f

2. In the process of converting normally gaseous hydrocarbons to gasoline motor fuel by heating normally gaseous hydrocarbons under high pressure to eilect substantial conversion thereof toliquid hydrocarbons including a gasoline fraction having a proportion of relatively light lowboiling normally liquid hydrocarbons including iso-olefin constituents which ordinarily constitute the light ends of gasoline which is in excess of the proportion of such low-boiling constituents` desired in a gasoline of satisfactory boiling characteristics, the steps of separating from the products oi said conversion operation normally liquid hydrocarbons substantially deiicient in said light 10W-boiling normally liquid hydrocarbons and a fraction consisting of substantial proportions of said light low-boiling normally liquid hydrocarbons and normally gaseous hydrocarbons having four carbon atoms per molecule and substantially free of hydrocarbons having less than four carbon atoms per molecule, subjecting said fraction to selective polymerization conditions to convert at least a portion of the iso-olens contained therein to higher boiling hydrocarbons Withlimited conversion of normal olens, and blending constituents of the reaction products of said selective conversion treatment with said normally liquid hydrocarbons decient in said light lowboiling normally liquid hydrocarbons to produce a gasoline motor fuel of desired boiling characteristics.

HAROLD V. ATWELL. 

